import random
import string


def GetRandomImgName():
    l = string.ascii_letters+string.digits
    ranLen = random.randint(15,22)
    #2、获取指定长度的字符串sample(a,b)
    # b的长度需小于等于a
    s = ""
    for i in range(1,3):
        s = s+l
    #通过join()方法连接字符
    GetStr =''.join(random.sample(s,ranLen))
    return GetStr